- General Investigations (prospecting)
- Exploration: a preliminary exploration, detailed exploration
- Feasibility study: technical, economic, environmental (including EIA study)
- Preparation of production (development, construction)
- Mining (Demolition, Upload, Transportation, Landfill)
- Reclamation and Environmental Management
- Processing (mineral dressing)
- Purification / extraction metallurgy
- Corporate Social Responsibility (CSR)
- Termination of Mine (Mine Closure)
Coal is one of fossil fuels. General understanding is sedimentary rock that can be burned, formed from organic deposits, primarily the remains of plants and formed through a process pembatubaraan. Its main elements consist of carbon, hydrogen and oxygen.
Coal is also an organic rock that has physical properties and chemical complexes that can be found in many forms.
Element analysis provides an empirical formula such as: bituminus and C137H97O9NS to C240H90O4NS for anthracite.
The formation of coal requires certain conditions and only occurs in certain eras in the history of geology. Carbon Age, approximately 340 million years ago (jtl), is the formation of the most productive coal where nearly all deposits of coal (black coal) is economically the northern hemisphere is formed.
In the Permian Period, about 270 jtl, also formed the coal deposits are economically in the southern hemisphere, like Australia, and goes on until the Tertiary Period (70 to 13 jtl) in various other hemisphere.
Coal formation material
Almost all the coal-forming plant. The types of coal-forming plants and the age by Diessel (1981) is as follows:
- Algae, from Pre-Cambrian era to the Ordovician and single-celled. Very few coal deposits of this period.
- Silofita, from the Silurian Period to the Middle Devonian, is derived from algae. Few coal deposits of this period.
- Pteridofita, Upper Devonian age to the Upper Carbon. The main subject of coal-forming age of carbon in Europe and North America. Flowers and plants without seeds, spores multiply and grow in warm climates.
- Gimnospermae, the period starting from the Permian Period to the Middle Cretaceous. Heterosexual plants, seeds wrapped in fruit, such as pine, contain levels of sap (resin) high. Type gangamopteris and Pteridospermae like glossopteris is the main constituent as Permian coal in Australia, India and Africa.
- Angiospermae, from the Upper Cretaceous period until now. Modern plants, fruit covering the seed, male and female in a single flower, less gummy than gimnospermae that, in general, less can be preserved.
- Based on the formation process that is controlled by pressure, heat and time, coal is generally divided into five classes: anthracite, bituminus, sub-bituminus, lignite and peat.
- Anthracite is the highest grade coal, with shiny black color (luster), metallic, containing between 86% - 98% of the elements carbon (C) with water content less than 8%.
- Bituminus containing 68 to 86% the element carbon (C) and water-yield 8-10% of the weight. Class the most coal mined in Australia.
- Sub-bituminus contains less carbon and a lot of water, and therefore a source of heat is less efficient than bituminus.
- Lignite or brown coal is a very soft coal containing 35-75% of water weight.
- Peat porous and has a moisture content above 75% and the value of the lowest calories.
The process of change remains of plants into peat to coal termed pembatubaraan (coalification). In summary, there are 2 stages of the process, namely:
- Stage Diagenetik or Biochemistry, begin at the plant materials until terdeposisi lignite formed. The main agents involved in this change process is the water content, the level of oxidation and biological disorder that can cause decay (decomposition) and kompaksi organic material and forming peat.
- Metamorphic stage or geochemistry, including the change process from lignite to anthracite bituminus and finally.
In Indonesia, coal deposits which have economic value in the Tertiary basin, located in the western part of Sundaland (including the island of Sumatra and Kalimantan), the general economic coal deposits can be classified as Eocene age coal or around the Lower Tertiary, about 45 million years ago and the Miocene or around Upper Tertiary, about 20 million years ago according to geological time scale.
Coal is formed from peat deposits on ancient climates around the equator, which is similar to present conditions. Some of them tegolong peat dome formed in the ground water level averages on wet climate throughout the year. In other words, the peat dome is formed in conditions where inorganic minerals which can be carried by water into the system and form a layer of coal ash and sulfur yield lower and thicken locally. This is very common in Miocene coal. In contrast, Eocene coal deposits are generally thinner, yield high ash and sulfur. Both age coal deposits are formed in lacustrine environments, coastal plain, or delta, similar to the formation of peat is happening today in the eastern regions of Sumatra and Kalimantan, mostly.
Eocene Coal Deposition
These sediments formed in the tectonic fabric that started around ekstensional Lower Tertiary or Paleogene in the hollows of sediment in Sumatra and Kalimantan.
Extension of this Eocene age occur along the edge of Sundaland, from the west Sulawesi, eastern Borneo, Sumatra, Java Sea up. Of sedimentary rock that once found can be seen that the precipitation runs from happening in the Middle Eocene. Lower Tertiary expansion occurred in Sundaland is interpreted to be the arc in the order, which is caused mainly by the movement penunjaman Indo-Australian Plate.  Environment early precipitation during the non-Paleogene was yesterday, especially fluviatil, and alluvial fan deposits a shallow lake.
In southeastern Kalimantan, coal deposition occurred around the Middle Eocene - Upper in Sumatra but a younger age, ie Upper Eocene to Lower Oligocene. In the middle part of Sumatra, fluvial deposits that occur in the early phase and then covered by sediments of the lake (non-yesterday).  In contrast to what happened in southeastern Kalimantan, where the fluvial deposits and is covered by a layer of coal that occurred in the coastal plain which is covered on top of sediment transgresif by Upper Eocene-old yesterday. 
Eocene coal sludge that has been commonly known occurs in the following basins: Sand and acids (South and East Kalimantan), Barito (South Kalimantan), Upper Kutai (East and Central Kalimantan), Melawi and Ketungau (West Kalimantan), Tarakan (Borneo East), Ombilin (West Sumatra) and Central Sumatra (Riau).
Below are the average quality of some coal deposits in the Eocene Basin Company Indonesia.Tambang total water content (% ar) inherent water content (% ad) ash content (% ad) Substance fly (% ad) Sulfur (% ad) Value energy (kcal / kg) (ad)
Acids Satui PT Arutmin Indonesia 10:00 7:00 8:00 41.50 0.80 6800
Sand Senakin PT Arutmin Indonesia 9:00 4:00 15:00 39.50 0.70 6400
Petangis Sand Kendilo PT BHP Coal 11.00 4.40 12.00 40.50 0.80 6700
Ombilin Ombilin PT Bukit Asam 12:00 6:50 <8:00>
Parambahan Ombilin PT Allied Indo Coal 4:00 to 10:00 (ar) 37.30 (ar) 0:50 (ar) 6900 (ar)
(ar) - as received, (ad) - the water dried, Source: Indonesian Coal Mining Association, 1998
Coal Miocene sediments
In the early Miocene, Lower Tertiary regional expansion - Central Sundaland has ended. At Kala Oligocene to early Miocene occurred yesterday at transgresi broad areas where sediment terendapkan yesterday klastik thick and perselingan sequences batugamping. Appointment and compression is a general appearance on Neogene tectonics in Borneo and Sumatra. Miocene sediments of the economic coal mainly located in the bottom of the Kutai Basin (East Kalimantan), Barito Basin (South Kalimantan) and the southern part of Sumatra Basin. Miocene coal mined economically also in Bengkulu Basin.
This coal is generally terdeposisi in fluvial environment, delta and coastal plain regions similar to the current formation of peat in the eastern part of Sumatra. Another key characteristic is the ash and sulfur levels are low. But most Miocene coal resources are classified as sub-bituminus or lignite that is less economical than if very thick (PT Adaro) or a favorable geographical location. But the Miocene coal at several locations are also classified as high grade as the mineral deposit Pinang and Prima (PT KPC), the coal deposits around the downstream Mahakam River, East Kalimantan and several locations near Tanjungenim, southern Sumatra Basin.
The table below shows the average quality of some coal deposits in the Miocene Basin Company Indonesia.Tambang total water content (% ar) inherent water content (% ad) ash content (% ad) Substance fly (% ad) Sulfur (% ad) The energy values (kcal / kg) (ad)
Kutai Prima Coal PT Kaltim Prima 9:00 to 4:00 39.00 0:50 6800 (ar)
Pinang Kutai PT Kaltim Prima Coal, 13:00 to 7:00 37.50 0:40 6200 (ar)
Roto South Pasir Jaya Agung PT Kideco 24.00 - 3.00 40.00 0:20 5200 (ar)
Binungan Tarakan PT Berau Coal 18:00 14:00 4:20 40.10 0:50 6100 (ad)
Lati Tarakan PT Berau Coal 24.60 16:00 4:30 37.80 0.90 5800 (ad)
Air Laya southern Sumatra, PT Bukit Asam 24.00 - 5:30 34.60 0:49 5300 (ad)
Paringin Barito PT Adaro 24.00 18:00 4:00 40.00 0:10 5950 (ad)
(ar) - as received, (ad) - the water dried, Source: Indonesian Coal Mining Association, 1998
The potential of coal resources in Indonesia is very abundant, especially on the island of Borneo and Sumatra, while in other regions, although the coal can be found in small amounts and can not be determined keekonomisannya, such as in West Java, Central Java, Papua, and Sulawesi.
In Indonesia, coal is the main fuel other than diesel fuel (diesel fuel) which has been commonly used in many industries, from coal economically much more efficient than diesel, with the following comparisons: Solar USD 0.74 / kilocalories while the coal is only Rp 0, 09/kilokalori, (based on industrial diesel prices USD. 6.200/liter).
In terms of the quantity of coal, including the most important fossil energy reserves for Indonesia. Very abundant in number, reaching tens of billions of tons. This amount is enough to supply the electrical energy needs of hundreds of years into the future. Unfortunately, Indonesia can not be burned coal and convert it into electricity through a steam power plant energis. In addition to pollutants contaminate the environment through CO2, SO2, NOx and CxHy this way made it less efficient and less high added value.
Coal should not be directly burned, will be more meaningful and efficient if it is converted into synthetic oil, or other petrochemical substances that high economic value. Two ways are considered in this case is likuifikasi (melting) and gasification (penyubliman) coal.
Burning coal directly (direct burning) has developed the technology in a continue, which aims to achieve maximum efficiency, methods such as direct combustion: fixed grate, chain grate, fluidized bed, pulverized, and others, each having strengths and weaknesses.
Coal gasification is a process to transform solid coal into coal gas flammable (combustible gases), after the purification process gases are CO (carbon monoxide), carbon dioxide (CO2), hydrogen (H), methane (CH4), and nitrogen (N2) - can be used as fuel. using only air and water vapor as the reacting gas-producing water and gas or coal gas, gasification has significantly the level of air emissions, solid waste and waste lowest.
However, coal is not a perfect fuel. Bound inside the sulfur and nitrogen, when coal is burned these impurities are released into the air, when floating in the air these chemicals can combine with water vapor (such as fog samples) and drops that fell to the ground sulfurite bad shape and nitric acid, referred to as "acid rain" "acid rain". Here also there is a small mineral stains, including common dirt mixed with coal, these small particles do not burn and create dust left in the coal combustor, a few small particles are also captured in the round of combustion gases along with water vapor, from the smoke coming from chimney some of these small particles is very small is equivalent to a human hair.
How to make clean coal
There are several ways. Examples of sulfur, sulfur is a chemical substance that is a little yellowish in coal, in some coal found in Ohio, Pennsylvania, West Virginia and other eastern states, consists of sulfur from 3 to 10% by weight of coal, some coals found in Wyoming , Montana and the states west of the other only about 1/100ths sulfur (less than 1%) of the weight of coal. It is important that most of the sulfur is removed before reach the chimney.
One way to clean coal is the easy way to break the coal into smaller chunks and wash them. Some sulfur is present as small dots in the coal called "pyritic sulfur" because it is combined with iron to form iron pyrite, otherwise known as "fool's gold" can be separated from coal. In particular the process of one-time, lump of coal put into in a large tank filled with water, coal floated to the surface when the dirt of sulfur sank. washing facilities are called "coal preparation plants" that clean-coal from the impurities.
Not all of the sulfur can be cleaned this way, however, is the sulfur in coal is actually chemically bound with carbon molecules, this type of sulfur-called "organic sulfur," and washing will not eliminate them. Several processes have been attempted to mix the coal with chemicals that liberate sulfur out of coal molecules, but most of these processes have proven too expensive, scientists are still working to reduce the cost of these chemical cleaning procedure.
Most modern power plants and all facilities built after 1978 - have been required to have installed special equipment to remove sulfur from combustion of coal gas before the gas is up to the chimney. This tool is actually a "flue gas desulfurization units," but many people called "scrubbers" - because they had scrub (scrubbing) of sulfur out of smoke released by coal-burning stove.
Discard NOx from coal
Nitrogen in general is a big part of the inhaled air, in fact 80% of air is nitrogen, normally nitrogen atoms bound to float to each other like chemical couples, but when the air is heated as in the boiler flame (F = 3000 1648 C), nitrogen atoms are split and bound with oxygen, forms as nitrogen oxides, or it is sometimes referred to as NOx. NOx can also be formed from the nitrogen atom trapped inside the coal.
In the air, NOx is a pollutant that can cause a hazy brown fog that sometimes appear around the major cities, as well as the pollution that forms "acid rain" (acid rain), and can help make something called "ground-level ozone", type Other than the pollution that can make the air dirty.
One of the best ways to reduce NOx formation is avoided from home, some have found ways to burn coal in fuller where there is more fuel than the air in the hottest combustion chamber. Under these conditions most of the oxygen combined with fuel than with nitrogen. The mixture was then sent to the combustion chamber of a second where there is a similar process repeated until all the fuel burned. This concept is called "staged combustion" because coal burned in stages. Sometimes referred to as "low-NOx burners" and has been developed that can reduce Nox in apart of air more than half. There are also new technology that works like "scubbers" that clean NOx from flue gases (smoke) of coal. Some of these devices use special chemicals called catalysts that break down the NOx into non-polluting gas, although this instrument is more expensive than "low-NOx burners," but can hit more than 90% of pollution Nox.